add a bootstrap variant of naked_asm

Author: folkertdev

core/src/arch.rs

@@ -3,6 +3,9 @@
 #[allow(unused_imports)]
 #[stable(feature = "simd_arch", since = "1.27.0")]
 pub use crate::core_arch::arch::*;
+#[unstable(feature = "naked_functions", issue = "90957")]
+#[cfg(bootstrap)]
+pub use crate::naked_asm;
 
 /// Inline assembly.
 ///
@@ -17,6 +20,37 @@ pub macro asm("assembly template", $(operands,)* $(options($(option),*))?) {
     /* compiler built-in */
 }
 
+/// Inline assembly used in combination with `#[naked]` functions.
+///
+/// Refer to [Rust By Example] for a usage guide and the [reference] for
+/// detailed information about the syntax and available options.
+///
+/// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html
+/// [reference]: https://doc.rust-lang.org/nightly/reference/inline-assembly.html
+#[unstable(feature = "naked_functions", issue = "90957")]
+#[macro_export]
+#[cfg(bootstrap)]
+macro_rules! naked_asm {
+    ([$last:expr], [$($pushed:expr),*]) => {
+        #[cfg(any(target_arch = "x86_64", target_arch = "x86"))]
+        {
+            core::arch::asm!($($pushed),*, options(att_syntax, noreturn))
+        }
+        #[cfg(not(any(target_arch = "x86_64", target_arch = "x86")))]
+        {
+            core::arch::asm!($($pushed),* , $last, options(noreturn))
+        }
+    };
+
+    ([$first:expr $(, $rest:expr)*], [$($pushed:expr),*]) => {
+        naked_asm!([$($rest),*], [$($pushed,)* $first]);
+    };
+
+    ($($expr:expr),* $(,)?) => {
+        naked_asm!([$($expr),*], []);
+    };
+}
+
 /// Inline assembly used in combination with `#[naked]` functions.
 ///
 /// Refer to [Rust By Example] for a usage guide and the [reference] for